Use of polymethylpentene film as release film in a method for shaping composite material

Abstract

The present invention relates to the use of a single layer polymethylpentene film as release film in a method for shaping a composite material.

1 . A method of shaping a composite material with a single layer polymethylpentene film as release film, wherein the method comprises:
 a) placing a substantially planar composite material between an upper polymethylpentene film and a lower polymethylpentene film by creating a pocket between the films which houses the composite material,   b) bringing the upper polymethylpentene film and the lower polymethylpentene film into intimate contact with the composite material, thereby forming a layered structure, wherein the composite material is held stationary between the upper polymethylpentene film and the lower polymethylpentene film until heat or force is applied to the layered structure;   c) optionally pre-heating the layered structure in a heating apparatus at a temperature sufficient to either lower a viscosity of the composite material or soften the upper and the lower polymethylpentene films;   d) positioning the layered structure in a press tool comprising a male mold and a corresponding female mold separated by a gap, wherein the male mold and the female mold each independently have a non-planar molding surface,   e) compressing the layered structure between the male mold and the female mold by closing the gap between the male mold and the female mold; and   f) maintaining the male mold and the female mold in a closed position until the viscosity of the layered structure reaches a level sufficient to maintain a molded shape.   
     
     
         2 . The method of  claim 1 , wherein the polymethylpentene film has
 melt temperature (T melt ) no less than about 205° C.,   thickness (t) in the range of about 10 microns to about 200 microns,   Elastic Modulus (E) in the range of about 400 to about 900 MPa,   Tensile Strength (σ) in the range of about 10 to about 50 MPa, and   elongation at break (ε) in the range of about 50 to about 550%, in either longitudinal or transverse directions at a rate of about 8 mm/s under ambient conditions.   
     
     
         3 . The method of  claim 1 , wherein step (e) comprises partially closing the gap between the male mold and the female mold such that a smaller gap is formed between the molds, which smaller gap is subsequently closed after a specific time or viscosity is reached. 
     
     
         4 . The method of  claim 1 , wherein the male mold and the female mold are maintained at a temperature above ambient temperature. 
     
     
         5 . The method of  claim 4 , wherein the male mold and the female mold are maintained at a temperature above 100° C. 
     
     
         6 . The method of  claim 4 , wherein the male mold and the female mold are maintained at a temperature between about 120° C. and about 160° C. 
     
     
         7 . The method of  claim 4 , wherein the male mold and the female mold are maintained at a temperature about 150° C. and about 190° C. 
     
     
         8 . The method of  claim 1 , wherein the polymethylpentene film is a recycled film. 
     
     
         9 . The method of  claim 1 , wherein step (e) comprises closing the gap between the male mold and the female mold at a speed of between about 0.7 mm/s and about 400 mm/s, while maintaining the male mold and the female mold at a temperature above a softening point of the composite material. 
     
     
         10 . The method of  claim 1 , wherein step (b) comprises applying a vacuum pressure of at least about 670 mbar between the upper film and the lower film. 
     
     
         11 . The method of  claim 1 , wherein the male mold and female mold are maintained in a closed position for between about 1 minute and about 60 minutes. 
     
     
         12 . The method of  claim 1 , wherein the upper film and the lower film are held together by a structural frame comprising a top frame, a center frame and a bottom frame, wherein:
 the lower film is held between the bottom frame and the center frame; and   the upper film is held between the center frame and the top frame.   
     
     
         13 . The method of  claim 12 , wherein the center frame supplies a source of vacuum to the assembly. 
     
     
         14 . The method of  claim 1 , wherein the upper film and the lower film are held together by a structural frame comprising a top frame and a bottom frame, wherein both the lower film and the upper film are held between the bottom frame and the top frame. 
     
     
         15 . The method of  claim 1 , wherein the layered structure is positioned in the press tool and in the optional heating apparatus by automated means. 
     
     
         16 . The method of  claim 1 , wherein the composite material comprises structural fibers of a material selected from aramid, high-modulus polyethylene (PE), polyester, poly-p-phenylene-benzobisoxazole (PBO), carbon, glass, quartz, alumina, zirconia, silicon carbide, basalt, natural fibers and combinations thereof. 
     
     
         17 . The method of  claim 1 , wherein the composite material comprises a binder or matrix material selected from thermoplastic polymers, thermoset resins, and combinations thereof.